Vintage Hi-Fi Audio Restorations: R Foerster's Pioneer SX-1000TW Restoration

Pioneer SX-1000TW Receiver

The TW version SX-1000 is different than its similar branded tube versions such as the TA and more akin to the all solid state TD version. An early SS Pioneer receiver produced in 1971.

W16-010 Reg. Power Supply

The regulated supply design employs a single 1A full wave rectification stage for the RF/Lighting functions as well as a 3A full wave bridge rectifier array for the AF and Driver stages with a slightly different type of filtering stage design for the 80V rails.

All of the rectifier diodes were replaced with robust 3A600V type axial Vishay and ultra-fast, soft recovery diodes in the full wave array. All of the small signal devices were replaced with high quality ZTX TO-92 style devices. All of the electrolytics were replaced with a high temp (105C), low impedance Nichicon PW type with an increase in DC decoupling stages for better filtering and increase in operating voltages.

BEFORE

AFTER

Reg. Vdc Confirmation

Filter Stage/Coupling

As mentioned above the two 1000MFD filters are in parallel with each other for the -/+B source as well as two 1000MFD capacitors used in the cap-coupled output stage for the driver design. These were all replaced with single high temp (105C) low impedance Nichicon PW type with a parallel combo for the -/+B filters at 100V rating.

BEFORE

AFTER

W15-089 Head Amp (RIAA)

The RIAA is a simplified cap coupled single-ended design with a quite accurate curve response.

All of the electrolytic were replaced with a low impedance PW and input/outputs replaced to Muse BP type Nichicons with an increase in operating voltages. DC decoupling capacitors were increased for better filtering. All of the small signal devices were replaced with modern, low noise Fairchild TO-92 devices.

BEFORE

AFTER

RIAA Curve Response

W15-090 Front End Amp

Similar to the head amp stage employing a single-end output design. Again, all of the electrolytic were replaced with a KT audio grade, low impedance PW and BP Nichicon capacitors with an increase in operating voltage and DC decoupling stages increased in MFD for better filtering. All of the small signal devices were replaced with modern, low noise Fairchild TO-92 devices. Several of the input/coupling mylar films were replaced with a high grade WIMA polypropylene film capacitors.

BEFORE

AFTER

W15-091 PA (Drivers)

Featuring a true single-ended output design with a push-pull internal. As with most of the unit a large cap-coupled output stage using the above mentioned 1000MFD devices and unique/oddball biasing scheme and thermistor piggy-back.

Initial differentials were replaced with modern low noise Fairchild TO-92 type, and later several other devices with high quality ZTK devices. All of the electrolytic were replaced with a low impedance PW Nichicon type and input to MUSE BP type all with an increase in operating voltages and DC decoupling capacitors for bettering filtering.

BEFORE

AFTER

Biasing Confirmations

RF Stages

All of the original electrolytic here were replaced with a Panasonic FC and low impedance PW types, including several small value and coupling stages with a high grade WIMA polypropylene film capacitors.

BEFORE